Process for creating designs on marble

ABSTRACT

There is disclosed a process for creating either a stippled or a striated effect on the surface of a piece of marble. The piece of marble is placed in an acidic solution and positioned so that the exposed surface of the slab faces downwardly. Gas bubbles which are evolved during the action of the acid on the slab remain in controlled contact with the exposed surface of the slab. When the exposed surface is placed facing down in a horizontal position, an eggshell effect is obtained and when the face of the surface is placed down and at an angle, a striated effect is obtained.

Donoho States Patent 1 Dec. 10,1974

1 1 PROCESS FOR CREATINQ DESIGNS ON MARBLE [75] Inventor: David W.Donoho, Baltimore, Md. [73] Assignee: vHilgartner Natural Stone Company,

' Inc., Baltimore, Md.

[22] Filed: Oct. 2, 1972 [21] Appl. No.: 294,191

[52] US. Cl. 156/2, 252/792 [51] llnt. C1. B44c 1/22 [58] Field ofSearch 156/2, 4, 5,7, 8, 14, 156/18; 252/792 [56] References CitedUNITED STATES PATENTS 1,081,290 12/1913 Albert 156/7 1,313,233 8/1919Grassuu.

1,775,384 9/1930 Beriau....

1,977,372 10/1934 Beriau 2,828,192 3/1958 Langsfeld 156/5 3,383,2545/1968 Kocsuta 156/5 3,483,049 12/1969 Grubbe 3,677,848 7/1972 Stolleret al. 156/17 [5 7] ABSTRACT There is disclosed a process for creatingeither a stippled or a striated effect on the surface of a piece ofmarble. The piece of marble is placed in an acidic solution andpositioned so that the exposed surface of the slab faces downwardly Gasbubbles which are evolved during the action of the acid on the slabremain in controlled contact with the exposed surface of the slab. Whenthe exposed surface is placed facing down in a horizontal position, aneggshell effect is obtained and when the face of the surface is placeddown and at an angle, a striated effect is obtained.

10 Claims, 6 Drawing lFigures PROCESS FOR CREATING DESIGNS ON MARBLEThis invention relates to a process for imparting a design to thesurface of a piece of limestone, and, more particularly, to the surfaceof a marble slab.

It is known that marble, which is a compact, granular, partlycrystalized form of limestone, may be etched by immersing it in anacidic solution. Thus, US. Pat. No. 1,977,372 discloses that a printingplate may be made by etching a marble block or slab in an acid solution.The bottom and sides of the marble slab are protected during the etchingby a coating of an acid resisting material, the top surface beingexposed. During the etching process, various colored parts of thesurface of the marble slab are etched at different rates than othercolored portions. This selective etching results in a surface havingraised portions thereon.

It is an object of the present invention to provide an improved processfor creating a decorative effect on the surface of a piece of alimestone.

It is another object of this invention to provide a process for creatingan eggshell or stippled effect on the surface of a marble slab.

It is a further object of this invention to provide a process forcreating a lined or striated effect on the surface of a marble slab.

These and other objects are accomplished by the practice of thisinvention, which, briefly, comprises providing a process whereby a pieceof limestone, e.g., a marble slab, is positioned in an acidic solutionso that gas bubbles which are evolved during the action of the acid onthe slab remain in controlled contact with an exposed surface of theslab. This is accomplished by positioning the exposed surface of theslab so that it does not face upwardly i.e., the exposed surface isplaced down either in a horizontal position or at an angle. When theexposed surface is placed facing down in a horizontal position, astippled effect is obtained, and if the face of the surface is placeddown and at an angle, a lined or striated effect is obtained.

The invention will be more particularly described by reference to theaccompanying drawings in which:

FIG. I is a semi-diagrammatic view illustrating the treatment of a pieceof marble according to one embodiment of the invention, the slab ofmarble being illustrated in side elevation:

FIG. 2 is a plan elevational view of the treated surface of the slab ofmarble showing the surface after treatment according to the methoddepicted in FIG. 1;

FIG. '3 is a fragmentary sectional view taken generally on line 3-3 ofFIG. 2;

FIG. 4 is a view similar to FIG. I illustrating the treatment of a slabof marble according to another embodiment of the invention:

FIG. 5 is a plan elevational view of the treated surface of the marbleslab after treatment according to the method depicted in FIG. 4; and

FIG. 6 is a fragmentary sectional view taken generally on line 66 ofFIG. 5.

In accordance with the practice of this invention, a marble stone orslab is placed in a solution of acid. The face of the slab must alwaysbe in the proper position in relation to the surface of the solution,since the angle of the stone in the solution determines the type offinish obtained. For best results, the stone should be flat and smooth.The degree of roughness on the surface of the stone affects the timerequired to produce a given finish. The acid in the solution may behydrochloric acid, nitric acid, phosphoric acid or any other acid havinga dissociation constant or ionization constant sufficiently high to etchmarble.

Referring specifically to FIG. 1, a marble slab 12 is positioned in theacidic solution Ill and is held off the bottom of the tank 10 by meansnot shown. For example, the slab may be secured by supporting meansattached to the top surface or it may be supported from underneath by ameans which will allow circulation of the acid which will permit theacid solution to contact the exposed surface. The exposed surface shouldbe kept off the bottom of the tank 10*. The slab I2 is positioned at anangle so that the exposed surface 13 is at an angle of about 45, asmeasured from the horizontal, and faces down. The upper surface of theslab and the ends of the slab are protected by a coating of anacidresisting material 14. The acid sollution l1.reacts with the exposedsurface 13 resulting in the evolution of gas bubbles 15. Since themarble slab contains areas of varying color, the lighter coloredportions are etched at a faster rate than the darker colored portions,thus resulting in a surface having raised portions 16 thereon as shownin FIGS. 2 and 3. The gas bubbles 15 which are evolved during theetching reaction seek to rise to the top of the acid solution 11.However, the bubbles 15 are not free to rise straight to the top fromthe point at which they are formed since they are in contact with andcovered by the surface 13. Accordingly, the bubbles 15 move upwardlyalong the slanted surface 13 until they reach the upper end 13a at whichpoint they leave contact with the surface and rise straight to the topof the acid solution 11 and escape to the surface at which point theymay be disposed of by conventional means. I

During the etching process, the acid solution which is in contact withthe surface 13 deteriorates i.e., it becomes weaker due to beingneutralized and loses its ability to etch the stone. As the gas bubbles15 move upwardly along the surface 13 in straight parallel lines, theymove away the deteriorated acid solution directly in their path and thisdeteriorated acid solution is replaced by fresh or undeteriorated acidsolution. Since fresh acid solution fills in behind the rising gasbubbles, the etching action in the path of the rising bubbles is morepronounced than in the adjacent areas which remain in contact withdeteriorated acid solution. This results in the path of the gas bubblesbeing etched to a greater extent than the adjacent areas, therebycreating lines or grooves 18 on the surface 13.

The width of the lines or grooves 18 will depend largely upon the angleof the stone in the acid solution 11 during the etching process. Thus,if the stone is placed at an angle of from to from vertical (at an angleof 0 the stone is vertical and at an angle of it is horizontal),relatively wide lines will be obtained whereas relatively fine lineswill be obtained when the stone is placed at an angle of from 30 to 45.In order to obtain more uniform widths of the lines from top to bottom,the position of the stone may be reversed halfway through the etchingprocess so that the relative positions of ends 13a and 13b as shown inFIG. 1 will be reversed.

An auxiliary source of gas bubbles may be provided to cause more bubblesto sweep upward along the surface 13 in order to reduce the timerequired to obtain the desired effect. Limestone chips may be placedunder the bottom of the slab 12. The action of the acid solution 11 onthe limestone chips will create additional gas bubbles. Alternatively,air may be injected into the tank under the bottom of the slab 12,resulting in air bubbles.

If'it is desired to lessen the effect of the gas bubbles on the exposedsurface of the stone, a gas suppressor such as gum arabic or methylcellulose may be added to the acid solution. The gas suppressorincreases the viscosity of the solution, thereby impeding the movementof the gas bubbles.

The final finish on the stone is affected by the acid content of thesolution, the ratio of the volume of the solution to the surface area ofthe stone, the duration of immersion of the stone in the acid solution,the position of the stone in the acid solution and the composition ofthe stone.

As shown in FIG. 4, a marble slab 20 of uniform white color is supportedby means not shown in a horizontal position (90) in the acid solution11. All surfaces of the slab are exposed to the acid solution. Gasbubbles which are evolved during the reaction of the acid solution onmarble are free to rise to the surface of the acid solution from the topand edges of the slab. However, gas bubbles 15 which are formed on theunderneath surface 21 are trapped against this surface for a timesufficient to cause a large number of very small, localized areas ofhigher etching action. This results in the production of stipples 22 onthe surface 21.

Marble which has been treated by the process of this invention may beused wherever a panel having a decorative effect is desired such as onthe walls of buildings.

The following examples illustrate embodiments of this invention:

EXAMPLE 1 A marble slab is placed in an acidic solution containing 32parts of water per part of concentrated (57%) nitric acid. The stone ispositioned at an angle of about 45 with the exposed surface facing downand above the bottom of the tank. The ends and the upper surface of thestone are masked with an acid resistant material. A continual stream ofgas bubbles is observed to rise to the top of the acid solution from apoint directly over the upper end of the slab. After about minutes, theposition of the slab is reversed so that the edge which was at the topis at the bottom, the exposed surface of the stone still being kept facedown. After about another 20 minutes, the stone is removed, washed withwater and polished by placing in a dilute acid solution. The exposedsurface of the treated stone contains a plurality of longitudinalgrooves which give it a lined or striated effect.

EXAMPLE 2 A piece of white marble is immersed in an acid solution asdescribed in Example 1. The stone is positioned at an angle of 90 i.e.,it is placed in a horizontal position so that the underside of the stoneis exposed to the acid solution. Gas bubbles are observed to rise fromaround all four edges of the stone. After about 45 minutes, the stone isremoved and washed with water. The bottom surface of the stone has astippled appearance.

I claim:

1. A process for creating a design on a piece of limestone whichcomprises positioning said piece of limestone in an acidic solution sothat the exposed surface of the piece faces downwardly and the gasbubbles which are evolved due to the reaction of the acid with the slabremain in controlled contact with the exposed surface of said slab.

2. A process as defined in claim 1 wherein said piece of limestone is aslab of marble.

3. A process as defined in claim 2 wherein an exposed surface of saidslab of marble faces down and is in a horizontal position whereby astippled effect is obtained.

4. A process as defined in claim 2 wherein an exposed surface of saidslab of marble faces down and is at an angle whereby a striated effectis obtained.

5. A process as defined in claim 4 wherein said exposed surface is at anangle of about 45.

6. A process as defined in claim 4 wherein said exposed surface is at anangle of from about to 7. A process as defined in claim 4 wherein saidexposed surface is at an angle of from about 30 to 40.

pressor is added to said acidic solution.

* l= l =l l

1. A PROCESS FOR CREATING A DESIGN ON A PIECE OF LIMESTONE WHICHCOMPRISES POSITIONING SAID PIECE OF LIMESTONE IN AN ACIDIC SOLUTION SOTHAT THE EXPOSED SURFACE OF THE PIECE FACES DOWNWARDLY AND THE GASBUBBLES WHICH ARE EVOLVED DUE TO THE
 2. A process as defined in claim 1wherein said piece of limestone is a slab of marble.
 3. A process asdefined in claim 2 wherein an exposed surface of said slab of marbLefaces down and is in a horizontal position whereby a stippled effect isobtained.
 4. A process as defined in claim 2 wherein an exposed surfaceof said slab of marble faces down and is at an angle whereby a striatedeffect is obtained.
 5. A process as defined in claim 4 wherein saidexposed surface is at an angle of about 45*.
 6. A process as defined inclaim 4 wherein said exposed surface is at an angle of from about 75* to85*.
 7. A process as defined in claim 4 wherein said exposed surface isat an angle of from about 30* to 40*.
 8. A process as defined in claim 4wherein the position of said slab of marble is reversed about halfwaythrough the process.
 9. A process as defined in claim 2 wherein anauxiliary source of gas bubbles is provided.
 10. A process as defined inclaim 2 wherein a gas suppressor is added to said acidic solution.